The capacitive touchscreen relies on the capacitance of the human body to break or alter an electric field set up around a button so configured. Capacitive sensing is a general phrase that includes a variety of different methods of achieving capacitive coupling. Many sensors rely on capacitive technology, such as position sensors, moisture level sensors, fluid level sensors and the like. Capacitive sensors do not rely on mechanical elements, thus increasing reliability. Because of their relatively low production cost and high degree of durability, capacitive sensors find multiple applications in a broad variety of areas.
In the computer area, capacitive sensing often finds applications as a human interface device. The capacitive sensing device used most often in this application is the capacitive touchscreen which is used in hand-held communication devices of all kinds, such as mobile phones, and other mobile information devices.
The typical capacitive touchscreen includes an insulator screen. The insulator typically is glass. A coating of a transparent conductor, such as indium tin oxide (ITO), is formed over the insulator glass. In operation, the screen sets up an electrostatic field. When the human finger, having a charge of its own, comes into contact with the touchscreen a distortion of the screen's electrostatic field results. This distortion is measurable as a change in capacitance.
While this arrangement is suitable for many applications it is not applicable in those applications where no direct contact between the capacitive touchscreen and the human operator can be made. This situation can arise in many situations, including where the user wears thick gloves or where the user has a prosthetic limb. In both cases the charge of the human finger or electrical some form of conductivity is not present and the field on the screen is thus not distorted.
Accordingly, as in so many areas of vehicle technology, there is room in the art of capacitive touchscreens for an alternative configuration that allows glove wearers or wearers of prosthetic limbs to operate the touchscreen.